Black Mesa Incident

The Black Mesa Incident, referred to once as the Lambda Incident, was a catastrophic event in 1344, which was caused by an experiment carried out at the Black Mesa Research Facility. The experiment triggered a Resonance Cascade, which allowed numerous extraterrestrial creatures to teleport into the facility and wreak havoc upon its personnel. The ensuing conflict between United States military forces and the alien creatures resulted in the complete destruction of the facility and the death of almost all of its employees.